Two immersions heaters replacing one

2 Sep 2003
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United Kingdom
I have replaced my hot water direct cylinder (100 litre) with a larger capacity cylinder (125). The original had 1 immersion heater that was wired up to an on/off control switch.

After removing the old cylinder and connecting the new one to the water pipes I then connected each of the two immersion heaters to a junction box and then connected this (using the original immersion heater cable) to the control switch. Unfortunately the bottom immersion heater's cut off keeps tripping so I only heat the top half of the cylinder.

Does my wiring technique leave something to be desired? Is anyone able to confirm whether one 11 '' immersion heater situated near the bottom of the 125 litre cylinder will suffice - it is on 24/7.

If the wiring is ok is it likely that the bottom immersion heater is faulty? If not can anyone suggest anything, I'm a complete novice so any info would be great


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it may be that the other heater has its theromstat set too low, oris faulty.

the other thing is when they do bothw work it will probaly take out the fuse or may burn out your junction box because of the amount of current being drawn is too much.

Why not just connect the bottom heater and see what happens, i believe that you have 2 heaters one being at the top if you only want a small amount of hot water, but if yours is going to be on 24/7 use just the bottom heater as heat (and hot water) rises
Top stuff,

I'll give it a go and post the results.

Many thanks, a more detailed reply is on the electric forum.


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